Electromagnetic radiation emitted from an external source can cause disturbances to an electrical circuit. Such disturbances are known as electromagnetic interference (EMI) or radiofrequency interference (RFI). The performance of the circuit may be interrupted, obstructed or otherwise degraded or limited by EMI. A variety of different objects may be the source of EMI, and may be naturally occurring or man-made.
EMI shielding consisting of conductive material surrounding an electronic device is used to create a Faraday cage which prevents electronic signals from penetrating into the enclosed space. Any opening, such as may exist around components that extend outwardly of the cage may create a break in the condition of the Faraday cage, and thereby undesirably allow the passing or emitting of interfering signals.
Components that extend outwardly of a main housing structure of an electronic device present particular problems when the component is movable relative to the main housing structure. Antennas are used to receive and transmit electromagnetic signals for the operation of electronic devices including televisions, radios, computers, medical instruments, business machines, communications equipment and the like. It is known for an antenna to be movable in one way or another relative to the main structure of the electronic device in which it operates. For example, antennas are known to be extendable and or rotatable relative to an electronic device, and therefore are the source of gaps in the EMI shielding of the device. Various types of conductive O-rings or elastic gaskets are known to be used around antennas or other movable components with some effectiveness. However, the integrity of such sealing devices can be compromised over time, diminishing the EMI shielding of the device. Further, the sealing devices may have inadequate flexibility to conform to the differing shape of an extendable antenna, for example.
What is needed in the art is a seal around externally movable parts of electronic devices that provides both EMI shielding and environmental sealing between the movable component and the main structure of the electronic device.